[v0] Accepted with modifications by phcoder@
[v1] Introduce subsections within Security
[v1] Correct errors regarding public key files not being automatically signature-checked in trust and verify_detached
[v1] Replace check_signatures=enforce with check_signatures set to enforce
[v1] Move detailed discussion of using signatures out of check_signatures environment variable description
[v1] Use long form for option flags to security-relevant commands
[v2] Explain the key fingerprint format for distrust and list_trusted.
[v2] Eliminates references to grub-mkimage and UEFI Secure Boot.
[v3] Updates in response to addition of --skip-sig to trust and verify_detached
[ ] Restore @xref for cross-references at the start of sentences
c16535a845
